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Abstract
Making accurate impressions of dental implants and transferring their three-dimensional (3D) position to master casts is critical for the passive fit of prosthetic frameworks. This study aimed to assess the effect of dental implant angulation on the dimensional accuracy of master casts. An acrylic model with 2 external hexagonal implants was used in this in vitro experimental study. The impressions of the model were made in 42 positions, with different angulation of the 2 implants, ranging from +15° to -15°, by means of the open-tray and closed-tray impression techniques, using a polyvinyl siloxane impression material. The spatial coordinates of the implants were measured on the X, Y and Z axes. The dimensional accuracy of the impressions made at different positions (parallel, convergent and divergent) and different angulation of the implants were determined. The data was analyzed using the one-way analysis of variance (ANOVA), Student's t test and Tukey's test. Casts with the lowest accuracy were obtained when the 2 implants were divergent by 25° (R = 1.1336). However, the position of the 2 implants had no significant effect on the dimensional accuracy of the master casts. The error rate was 0.4181 in the open-tray technique and 0.5095 in the closed-tray technique, with no significant difference between them (p > 0.05). The angulation of the 2 implants had a significant effect on the dimensional accuracy of the master casts (p = 0.0001). Considering the significant effect of implant angulation in the range from +15° to -15° relative to the longitudinal axis on the dimensional accuracy of master casts, further studies are required to reach a final conclusion in this respect.
Highlights
Dental implants are presently in high demand
The position of the 2 implants had no significant effect on the dimensional accuracy of the master casts.The error rate was 0.4181 in the open-tray technique and 0.5095 in the closed-tray technique, with no significant difference between them (p > 0.05)
The angulation of the 2 implants had a significant effect on the dimensional accuracy of the master casts (p = 0.0001)
Summary
Dental implants are presently in high demand. Due to the high success rate of implant treatment, implantsupported restorations are the first choice for prosthetic treatment.[1]. Precise clinical and laboratory steps are taken to achieve passive fit.[2] Misfit would cause internal stresses, and their subsequent transfer to implants and the bone matrix.[3] In the fabrication of implant-supported restorations, the accurate transfer of the intraoral position of the implant to the cast is much more important than it is for natural teeth.[4] In these restorations, the applied physiological forces are transferred to the surrounding bone in a manner that is similar to what occurs in natural teeth.[5] due to the absence of the periodontal ligament around a dental implant, misfit can result in destructive stresses in the bone–implant complex.[3] evidence shows that the absence of passive fit in implant-supported restorations can cause tiny bone fractures or ischemic marginal zones. Making accurate impressions of dental implants and transferring their three-dimensional (3D) position to master casts is critical for the passive fit of prosthetic frameworks
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